April 25, 2014 - 3:00pm - 4:00pm
Title: Trefoil Knotted Polymer via Supramolecular Template Method and Ring-Expansion Strategy
Knots had gained keen interest from arts and mathematics because of their pretty and fascinating structures, and they were recently found in DNA and proteins by biologist.[1, 2] The present chemists are also motivated by their synthetic challenge, inherent structural beauty, and possible special properties. Thanks to the development of coordination chemistry and new method of covalent bond formation, successful syntheses of molecular trefoil knots and pentafoil knots were demonstrated recently.[4, 5]
Polymers with topologically interesting structures showed great potential applications by tuning the macromolecular properties.[6, 7] Polymers with topologically interesting structures like cyclic polymer and catenated polymer were synthesized by different strategies and their distinct properties, such as reduced hydrodynamic radii and lower viscosity compared to their linear analogues, were well studied, which exhibited great application potentials.[8, 9] Synthesis of knotted polymer represents a challenging chemical target that until now, no reasonable synthesis scheme has been reported, although its formation was claimed in polymer systems, often involving creativity and luck during end-to-end ring closure of linear chain precursor.[10, 11] Herein, a high yield synthesis of trefoil knotted polymer via supramolecular template method and ring-expansion strategy was reported. The expected properties compared to its linear analogue such as reduced hydrodynamic radii and lower intrinsic viscosity, together with an atomic microscopy (AFM) image of individual molecular knots, confirmed the formation of the resulting trefoil knotted polymer.
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